Sequential fully implicit well model for reservoir simulation

Abstract

A subsurface hydrocarbon reservoir with wells is simulated by sequential solution of reservoir and well equations to simulate fluid flow inside the reservoir and well production rates. Sequential solution of reservoir and well equations treats wells as specified bottom hole pressure wells. This avoids solving large matrices resulting from the simultaneous solution of the reservoir and well equations which can be computationally very expensive for large number of unknowns and require special sparse matrix solvers. Such sequential solution involves regular reservoir system solvers complemented by a small matrix for the numerical solution of the well bottom hole pressures.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS[0001]The present application is a continuation of, and claims priority to, co-pending, commonly owned U.S. patent application Ser. No. 13 / 023,728, filed Feb. 9, 2011.BACKGROUND OF THE INVENTION[0002]1. Field of the Invention[0003]The present invention relates to computerized simulation of hydrocarbon reservoirs in the earth, and in particular to simulation of flow profiles along wells in a reservoir.[0004]2. Description of the Related Art[0005]Well models have played an important role in numerical reservoir simulation. Well models have been used to calculate oil, water and gas production rates from wells in an oil and gas reservoirs. If the well production rate is known, they are used to calculate the flow profile along the perforated interval of the well. With the increasing capabilities for measuring flow rates along the perforated intervals of a well, a proper numerical well model is necessary to compute the correct flow profile to match th...

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Problems solved by technology

However, for highly heterogeneous reservoirs with some vertically non-communicating layers, the above-mentioned well models cannot produce the correct physical solution.

Instead, they produce incorrect flow profiles and in some occasions causes simulator convergence problems.

For wells with many completions and many wells in a simulation model, this method has become computationally expensive in terms of processor time.

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